Condenser pressure control apparatus

ABSTRACT

Non-condensable gas in a storage chamber is introduced into a refrigeration system to maintain condenser pressure above a desired minimum, and is permitted to escape from the refrigeration system back to the storage chamber to relieve high condenser pressures. Pressure responsive switches monitor the high side of the refrigeration system and control the flow of the non-condensable gas into and out of the refrigeration system.

United States Patent 1 Garland June 5, 1973 CONDENSER PRESSURE CONTROLAPPARATUS Milton W. Garland, Waynesboro, Pa.

Assignee: Frick Company, Waynesboro, Pa.

Filed: Sept. 3, 1971 Appl. No.: 177,548

Inventor:

US Cl. ..62/85, 62/149, 62/174, 62/196 Int. Cl ..F25b 41/00 Field ofSearch ..62/l95, 196, 149, 62/174, 85, 475

References Cited UNITED STATES PATENTS 9/1960 Etherington ..62/1493/1970 Norton ..62/1 74 Primary ExaminerMeyer Perlin Attorney-A. YatesDowell, Jr.

[57] ABSTRACT Non-condensable gas in a storage chamber is introducedinto a refrigeration system to maintain condenser pressure above adesired minimum, and is permitted to escape from the refrigerationsystem back to the storage chamber to relieve high condenser pressures.Pressure responsive switches monitor the high side of the refrigerationsystem and control the flow of the non-condensable gas into and out ofthe refrigeration system.

6 Claims, 2 Drawing Figures CONDENSER PRESSURE CONTROL APPARATUSBACKGROUND OF THE INVENTION 1. Field of the Invention This applicationrelates to control of pressures within the high side of a refrigerationsystem. Specifically, it relates to apparatus for introducing anon-condensable gas into the high side of a refrigeration system andpermitting the escape of the same from the system in order to maintaincondenser pressure at a desired level.

2. Description of the Prior Art Various methods for controlling pressurewithin the high side of refrigeration units have been devised toincrease the efficient functioning of such units. In the US Pat. No.3,499,298 to Norton, a non-condensable gas is stored under pressure in achamber which is connected to the high side of a refrigeration apparatusby a fluid line. During normal operation, the fluid line is continuouslyopen. Thus, no automatic means is provided to relieve condenser pressureby isolating the non-condensable gas from the refrigeration unit.

SUMMARY OF THE INVENTION The present invention is an apparatus forcontrolling condenser pressure in a compression refrigeration unit. Astorage tank for non-condensable gas is provided together with fluidlines which connect the storage tank to the refrigeration unit. Pressureresponsive switches monitor condenser pressure in the refrigeration unitand operate control valves which regulate gas flow through the fluidlines. When condenser pressure falls to a desired minimum, a pressureswitch causes a first valve to open and permit introduction ofnoncondensable gas into the high side of the refrigeration unit therebyraising the condenser pressure. This valve is closed by the pressureswitch when condenser pressure rises to a predetermined level.

When condenser pressure rises to a desired maximum, a pressure switchcauses another pressure valve to open and permit the flow ofnon-condensable gas from the high side of the refrigeration unit backinto the storage tank thereby relieving condenser pressure. This valveis closed when condenser pressure falls to a predetermined level whichindicates that substantially all of the non-condensable gas butsubstantially none of the refrigerant vapor has passed out of therefrigeration unit. Non-condensable gas may not again reenter therefrigeration unit until condenser pressure drops to the desired minimumat which the first valve is caused to open. When the non-condensable gasis thus isolated, it cannot operate to boost condenser pressures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing theinvention. FIG. 2 is an electrical diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT A refrigeration system as shownin FIG. 1 has a compressor powered by an electric motor 28. Thecompressor draws refrigerant vapor through suction line 1 1 anddischarges it into line 12 on the high side of the system. The vapor isliquefied in condenser 13 and passes through line 15 to receiver 16.From the bottom of the receiver 16 the flow is through line 17 andexpansion valve 19 into the low side of the system including evaporator20, evaporator discharge line 22, and suction line 11. When thecompressor is shut off, a solenoid controlled valve 21 in fluid line 17is closed in order to keep the evaporator 20 from becoming flooded.

In accordance with the invention, a condenser pressure maintainingdevice is incorporated in the refrigeration system described above. Thepressure maintaining device includes a reserve tank 33 which isinitially charged with a stable non-condensable gas, such as drynitrogen. The pressure of the non-condensable gas in the reserve tank 33is less than the desired maximum condenser pressure, for example, lessthan 200 PSIG but greater than the rated evaporator pressure of forexample 50 PSIG in a refrigeration system using freon 22. The volume ofthe reserve tank 33 is large enough so that when the non-condensable gasis introduced into the refrigeration system, the reserve tank pressuredoes not drop to 50 PSIG. Accordingly, the reserve tank volume may, forexample, equal the sum of the volumes of the condenser 13 and receiver16 with a non-condensable gas pressure of 150 PSIG.

A fluid line 35 connects the top of the reserve tank to the compressorsuction line 11. Gas flow through line 35 is controlled by a solenoidoperated valve 37 in line 35. A second fluid line 32 connects the top ofreserve tank 33 to the top of the receiver 16. A solenoid operated valve39 controls flow through line 32. An adjustable pressure operated switch38 is provided to monitor condenser pressure and accordingly is suitablyconnected in line 32. This switch controls the operation of solenoidvalve 37. Similarly a second adjustable pressure switch 40 is providedto monitor the pressure in line 32 and to operate solenoid valve 39. Apressure gauge 34 is provided to monitor the reserve tank 33. Thus thepressure maintaining device, according to the invention, provides areserve compartment for noncondensable gas under pressure and such gasmay pass out of the reserve tank through line 35 to the suction line 11or into the reserve tank through a receiver attached line 32.

FIG. 2 shows the electrical hookup for the refrigeration system andpressure maintaining device discussed above. Lines 41 and 42 are powerlines which are connected by a pair of lines 43 and 44. In line 43 arelocated in series a master control switch 45, a thermostat switch 46, amotor 28, and motor overload breakers 47 and 48. Along the line 44 arearranged in series a pair of contacts 49 that close when the motorbegins operation, and a relay coil 50. The relay coil 50 operatesassociated relay contacts 51, 52 and 53.

A line 54 is interposed in line 44 between contacts 49 and relay coil 50and has three branch lines 55, 56 and 57 connected to power line 42.Solenoid 60 for operating valve 21 is located in branch line in serieswith relay contact 51. Solenoid 61 for operating valve 37 is located inbranch line 56 in series with relay contact 52 and pressure switch 38.Solenoid 62 for operating valve 39 is located on branch line 57 inseries with relay contact 53 and pressure switch 40.

The refrigeration system is started by closing master control switch 45so that current may pass between lines 41 and 42 through thermostatswitch 46, normally closed at high temperatures, through compressormotor 28 activating the same, and through normally closed motor overloadbreakers 47 and 48. When motor 28 starts operation, contacts 49 closethus activating relay coil 50 which closes associated relay contacts 51,52 and 53. Current flows through solenoid causing the valve 21 to openand also flows through to pressure activated switches 38 and 40 inseries with solenoids 61 and 62 which operate valves 37 and 39,respectively.

During a certain period of the year, such as winter, ambient airtemperatures surrounding the condenser 13 may be so low as to causepressure within the high side of the refrigeration unit, i.e., condenserpressure, to fall below a desired minimum, as for example, below 150PSIG. Below 150 PSIG, an insufficient pressure differential acrossexpansion valve 19 exists and tends to deprive the evaporator ofrefrigerant.

At a preselected pressure of, say, 150 PSIG, pressure switch 38 is setto close causing the solenoid valve 37 to open so that thenon-condensable gas in reserve chamber 33 is permitted to pass intosuction line 11. The compressor pumps the non-condensable gas into thehigh side together with refrigerant vapor from discharge line 22. In thehigh side the non-condensable gas displaces refrigerant vapors therebyraising the condenser pressure. As the refrigeration system continues tooperate, the non-condensable gas moves through the condenser andaccumulates in receiver 16 having a possible exit only through closedline 32 which leads back into the reserve tank 33.

After pressure within the high side of the refrigeration unit rises to apredetermined level, for example, about 160 PSIG, the pressure switch 38is set to open and cause the solenoid valve 37 to close, thus stoppingthe flow of non-condensable gas from the reserve tank 33 into thesuction line 11. Thus the partial pressure of the non-condensable gasintroduced into the high side raises the condenser pressure by 10 poundsfrom 150 P816 to 160 PSIG.

During summer, for example, high temperature ambient air conditions maycause condenser pressure to increase to 180 P810 or higher. At apreselected pressure of, say, 180 PSIG, the'pressure switch 40 is set toclose causing solenoid valve 39 to open thereby relieving condenserpressure and allowing non-condensable gas trapped in the top of thereceiver 16 to pass through line 32 and into the reserve tank 33.Solenoid valve 39 remains open continuously when ambient temperatureconditions maintain a condenser pressure of 180 PSIG or higher therebyrelieving condenser pressure into the reserve tank 33.

When solenoid valve 39 is open for an extended time, the pressureswithin the reserve tank 33 and receiver 16 tend to equalize. However, ifsubstantially all of the non-condensable gas in the receiver has passedinto the reserve tank but the reserve tank pressure is insufficient tobalance the receiver pressure, refrigerant vapor may pass through line32 and into the reserve tank until generally equal pressures areachieved. As condenser pressure decreases, refrigerant vapor within thereserve tank passes back into the receiver 16 since vapor pressurewithin the receiver 16 is lower than vapor pressure in the reserve tank33. The noncondensable gas, however, tends to remain in the reserve tank33.

After pressure within the high side of the refrigeration system falls apredetermined amount, for example, in this embodiment of the inventionapproximately 10 pounds below 180 PSlG to 170 PSIG, pressure switch dilis set to open thereby causing solenoid valve 39 to close and shut offthe flow of gas from the receiver 16 into the reserve tank 33 throughline 32. Note that the pressures without the pressure boosting effect ofthe non-condensable gas until the condenser pressure again drops to PSIGat which solenoid valve 37 is set to open. Compressor power requirementsand wear on the various parts of the refrigeration system are decreasedaccordingly.

I claim:

1. In a refrigeration system having a high pressure side and a lowpressure side, means for raising the pressure of refrigerant fromv thelow pressure side to the high pressure side, and means for condensingand receiving condensed refrigerant in the high pressure side, theimprovement comprising, means for maintaining the level of pressure inthe condensing and receiving means within a predetermined range, saidpressure level maintaining means comprising storage vessel means havinga first connection to the low pressure side adjacent to the pressureraising means and a second connection to the receiving means, a gaswhich is noncondensable in the system within the storage vessel means,and first and second valve means for selectively opening and closingsaid first and second connections to permit selective release of thenon-condensable gas from the vessel means into the pressure raisingmeans for discharge into the condensing and receiving means when thepressure level therein is relatively low in order to raise it and forrelease of said gas from the receiving means back into the vessel meanswhen the pressure level in the condensing and receiving means isrelatively high in order to lower it.

2. The invention as defined in claim 1 in which the volume of thestorage vessel means is sufficiently large to maintain the pressure ofsaid non-condensable gas in said storage vessel means below a minimumpressure required for proper refrigerant flow from the high pressureside to the low pressure side, and above a rated low side pressure whenthe first and second valve means are selectively opened and closed.

3. The invention as defined in claim 1, and means responsive to thepressure in said receiving means for opening and closing said first andsecond valve means.

' 4. The invention as defined in claim 1, first and second meansresponsive to the pressure in said receiving means, means connectingsaid first pressure responsive means to said first valve means and meansconnecting said second pressure responsive means to said second valvemeans, whereby said first and second valve means are automaticallyoperated in response to the pressure in said receiving means.

5. A compression refrigeration system having a high side and a low side,

a storage chamber for non-condensable gas, first and second fluid linesconnecting said refrigeration system to said storage chamber,

first means responsive to a predetermined low pressure in said high sidefor opening said first fluid line and permitting entry of saidnon-condensable gas into said high side to raise pressure in said highside above such predetermined low pressure, said first pressureresponsive means operative to close said first fluid line at a selectedpressure in said high side above said predetermined low pressure,

second means responsive to a predetermined upper pressure in said highside for opening said second fluid line to relieve pressure and permitescape of non-condensable gas from said high said when said high sidepressure is above said selected pressure, said second pressureresponsive means operative to close said second fluid line at a pressurein said high side below said pressure at which said second fluid line isopened but above said selectedpressure.

6. The method of controlling the range of pressure level in the highside of a refrigeration system having a compressor and a low side,comprising providing an auxiliary housing for a non-condensable gas,continuously sensing the level of pressure in the high side, withdrawingnon-condensable gas from the auxiliary housing into the low side,through the compressor and into the high side when the pressure level inthe high side is below a predetermined level only to the extentnecessary to. raise the pressure to a predetermined operating level, andwithdrawing the non-condensable gas from the high side directly into theauxiliary housing in response to a level of pressure in the high sidewhich is above a predetermined level.

IF i

1. In a refrigeration system having a high pressure side and a lowpressure side, means for raising the pressure of refrigerant from thelow pressure side to the high pressure side, and means for condensingand receiving condensed refrigerant in the high pressure side, theimprovement comprising, means for maintaining the level of pressure inthe condensing and receiving means within a predetermined range, saidpressure level maintaining means comprising storage vessel means havinga first connection to the low pressure side adjacent to the pressureraising means and a second connection to the receiving means, a gaswhich is non-condensable in the system within the storage vessel means,and first and second valve means for selectively opening and closingsaid first and second connections to permit selective release of thenon-condensable gas from the vessel means into the pressure raisingmeans for discharge into the condensing and receiving means when thepressure level therein is relatively low in order to raise it and forrelease of said gas from the receiving means back into the vessel meanswhen the pressure level in the condensing and receiving means isrelatively high in order to lower it.
 2. The invention as defined inclaim 1 in which the volume of the storage vessel means is sufficientlylarge to maintain the pressure of said non-condensable gas in saidstorage vessel means below a minimum pressure required for properrefrigerant flow from the high pressure side to the low pressure side,and above a rated low side pressure when the first and second valvemeans are selectively opened and closed.
 3. The invention as defined inclaim 1, and means responsive to the pressure in said receiving meansfor opening and closing said first and second valve means.
 4. Theinvention as defined in claim 1, first and second means responsive tothe pressure in said receiving means, means connecting said firstpressure responsive means to said first valve means and means connectingsaid second pressure responsive means to said second valve means,whereby said first and second valve means are automatically operated inresponse to the pressure in said receiving means.
 5. A compressionrefrigeration system having a high side and a low side, a storagechamber for non-condensable gas, first and second fluid lines connectingsaid refrigeration system to said storage chamber, first meansresponsive to a predetermined low pressure in said high side for openingsaid first fluid line and permitting entry of said non-condensable gasinto said high side to raise pressure in said high side above suchpredetermined low pressure, said first pressure responsive meansoperative to close said first fluid line at a selected pressure in saidhigh side above said predetermined low pressure, second means responsiveto a predetermined upper pressure in said high side for opening saidsecond fluid line to relieve pressure and permit escape ofnon-condensable gas from said high said when said high side pressure isabove said selected pressure, said second pressure responsive meansoperative to close said second fluid line at a pressure in said highside below said pressure at which said second fluid line is opened butabove said selected pressure.
 6. The method of controlling the range ofpressure level in the high side of a refrigeration system having acompressor and a low side, comprising providing an auxiliary housing fora non-condensable gas, continuously sensing the level of pressure in thehigh side, withdrawing non-condensable gas from the auxiliary housinginto the low side, through the compressor and into the high side whenthe pressure level in the high side is below a predetermined level onlyto the extent necessary to raise the pressure to a predeterminedoperating level, and withdrawing the non-condensable gas from the highside directly into the auxiliary housing in response to a level ofpressure in the high side which is above a predetermined level.